Hydraulic door opener



0t.1,1957 LANDERT 2,808,256

HYDRAULIC DOOR OPENER 0dn 1,1957 HLANDERT 2,808,256

HYDRAULIC DOOR OPENER f//l/ll/l,Izzi/111111111111 Oct l, 1957 u H, LANDERT 2,808,256

HYDRAULIC DOOR OPENER Filed March 23, 195s 4 sheets-sheet :s

HYDRAULIC DGGR OPENER Heinrich Landert, Bulach, Zurich, Switzerland Application March 23, 1956, Serial No. 573,398

Claims priority, application Switzerland March 29, 1955 17 Claims. (Cl. 268-64) The invention relates to hydraulic door openers which provide an adjustment of the opening angle of the door. Hitherto it has been the usual practice to adjust this opening angle in la stepwise manner by alternatively using dilerent groups of discharge ports of the hydraulic servomotor of the said door openers.

It is a main object of the present invention to provide a hydraulic door opener in which the opening angle of the door may be adjusted in a continuous manner.

With this and other objects in view I provide a hydraulic door opener, comprising in combination: an electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a cylinder in uid communication with the said pump and a piston moveable in the said cylinder and which is arranged to be mechanically coupled to the door, the said electric motor when energised driving the said pump and the latter then supplying iluid under pressure to the said servo-motor in the sense of opening the door, a spring mechanically connected to the said servo-motor and biasing the said piston thereof in the sense of closing the door, a normally closed valve arranged in fluid communication with the pressure side of the said cylinder, a normally open Valve arranged in fluid communication with the suction side of the said cylinder each of the said valves having a seat and a closure member moveable relative to its seat in a direction parallel to the movement of the said piston in the said cylinder, and adjustment means each in operative relationship to one of the said valves, one of the said adjustment means opening the said normally closed valve upon the said piston reaching a pre-determined position `and thus allowing the discharge of iluid from the pressure side of the said cylinder, and the other one of the said adjustment means closing the said normally open valve at approximately the same position of the said piston and thus stopping the discharge of llui'd from the section side of the said cylinder, the said position of the servo-motor piston corresponding to an aperture of the door predetermined by the setting of the said adjustment means.

By making the said adjustment means continuously adjustable, for example as abutment screws, the opening angle of the door is likewise made continuously `adjustable.

These and other objects and features of my said invention will be clearly understood from the following description of two embodiments thereof given by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a front elevation of the door opener according to a rst embodiment of the invention the cover Ahood thereof being assumed transparent and the outer linkage being omitted for clarity,

Fig. 2 is a section on line 2 2 of Fig. l, to which correspond the lines 2 2 of Figs. 4 to 8,

Fig. 3 is a section substantially on the line 3 3 of Fig. l, this section being however, not taken on the same level throughout for clarity, but as indicated by the lines 3 3 in Figs. 4 to 8, respectively,

2,@,255 Patented Get. l, 1957 Figs. 4, 5 and 6 are three cross sections on the lines 4 4, 5 5 and 6 6, respectively, of Figs. 2 and 3,

Fig. 7 is an end elevation of the pump casing of the door opener, as viewed in the direction of the arrow 7 in Fig. 2, the cylinder casing thereof being removed,

Figs. 8 and 9 are two cross sections on the lines 3 8 and 9 9, respectively, of Figs. 2 and 3.

Fig. l0 is a modification in detail of a valve in a section corresponding to part of Fig. 3, on a larger scale,

Fig. l1 is a section of another embodiment, similar to Fig. 3, andron a larger scale.

The door opener illustrated in Figs. 1V to l0 comprises an induction motor 10 (Fig. 2) which is electrically connected to a control apparatus (not shown) through terminals 11, Iarranged in a terminal box 12 (Fig. l), and a cable 13. This control apparatus may include for example photo-electric cells, lloor contact detector actuators, time switches or like well known means. When the electric motor 10 is energized, it drives a pump 14 (Fig. 2); the hydraulic fluid then acts in a manner to be explained later in more detail on a piston 16 arranged in a servo-motor cylinder 15, and moves the'same in the illustration of Fig. 3 from right to left. The tooth rack gearing 17 provided on the piston meshes with a spur gearing 18a provided on a spindle 18, and consequently turns the same. On top of saidspindle is mounted a linkage 19 (Fig. 5), such as has been described inV U. S. Patent No. 1,311,184 to J. H. Shaw, by means of which the door is opened.

For the closing of the door a spiral spring 2li is provided, which is loaded when the door is opened, the said spring being attached at one end to the said spindle 1S and at the other end to a sleeve 21. This sleeve isheld in position by screws 22 fixing a ring 23 to a casing portion 26, which ring bears on a shoulder of sleeve 2l. When the said screws 22 yare loosened, the sleeve 21 can be turned, and the loading of the spring 2li can be adjusted thereby, and iiXed by retightening the said screws 22.

VThe .electric motor 10, the pump 14- and the servomotor cylinder 15 are enclosed in a container, theV external walls of which are formed by casing portions 24, 25 and Y26, which enclose the said motor 1t), pump 14 and cylinder 15, respectively. The casing portion 26 for the cylinder V15 has a lid 26a which is fixed, with a gasket (not shown) interposed, by means of screws on the adjacent casing portion. The holes provided for these screws (not shown) in the lid 26a are indicated in Fig. 4 at 27.

The casing portions 24, 25, 26 are held together, with gaskets (not shown) interposed, by means of live screw bolts 28 (Fig. 9), the threaded ends of which are screwed into tapped holes (not shown) of the casing portion 26 vcontaining the cylinder. The heads of these screw bolts are likewise omitted in order to avoid encumbering the drawing.

Three screw holes 30 (Fig. l) .are provided forfastening the door opener on the door diagrammatically indicated in Fig. 2 at 29. The screws themselves are not shown. The casing 24 to 26 is covered by a hood`31, which is mounted thereon by means of screws 32.

The electric motor 1l) has a shaft 33 which is journalled at one end in a bushing 34 mounted in a bore 35 ofthe casing portion 24. This bore is closed from outside, with `a gasket (not shown) interposed, by means of a plugV 36. The other end of the shaft is provided with a coupling slot 37, into which engages a corresponding coupling projection 38 of a pump shaft 39. Both shafts 33 and 39 arejournalled in a common bore 40 ofthat portion 25 of the pump casing which serves as a mounting board for the motor.

The stator winding 42 of the electric motor 10 is electrically connected by insulated conductors 41 to the said terminals 11. The stator lamnations; 43 and the laminations 4d of the short-circuited rotor of the motor 10 are held together in the usual manner (not shown).

In the pump casing portion 25' a pumprotor 45 is enclosed, which is not shown in detail, and may be of the kind of a rotary eccentric feeder pump. A lid 46 is fixed to said casing portion by means of screws 46a. A suction duct 47, through which hydraulic fluid is sucked from a pressureless reservoir 4,3, Vis left clear in the pump casing portion 25. A further duct 49, `which issues into ythe pressure chamber 5? ofthe said servo-motor cylinder 15, is formed by two juxtaposed grooves in the adjacent end faces of the pump casing portion 25 Vand the cylinder casing portion 26 (Figs. 2, 3, 7). v Y

AAt the pressure side of the pump 45, the direction of Adischarge of which is indicated in theFigures by arrows, there is a non-return valve with a closure ball 5,1 and having anannular chamber 52 whichis connected Yto the entry 'into the aforesaid conduit 49. From the, pressure side of the pump the hydraulic fluid canreturn via an adjustable throttle bypass 53 to the pressureless reservoir 48.V The throttling point is located betweenan adjustment spindle 54 and a bore 55 from which the spindle may be retracted more or less, since itis screwed into a tapped bushing 55a. By adjustment of the throttle by# pass the speed of opening ofthe door' can be controlled.

At theV pressure side of the pump thereis moreover located in a chamber 56 the upper end of a plunger 57 v(Fig. 8) of a differential valve, the closure ball of which .is denoted 53. The space v59V surrounding the lower end Vof the plunger 57 (Fig. 8) is 'in communication in a manner not shown in detail with the pressureless reservoir Y48. As long as the pump operates, the `said plunger forces the ball 5S into the closure position, so that no liquid can pass from a conduit 6d controlled by it into the'pressureless reservoir 48. An abutment pin 61 limits the movement of the .plunger 57 in the upward direc# tion.

. When the pumpdoes not operate and the piston 16 moves under the action of the spring Ztlin the cylinder (Fig. 3) from left to right, the liquid flows from the pressure space Sti through two adjustable damping Vthrottles 62 and 63 arranged in parallel and through the aforesaid duct 60, and after lifting the ball 58 and plunger 57 of the differential valve (Fig. 8), passes into the vpressureless reservoir 4S. The Vthrottles 62 and 63 are constructed similarly' to the throttle by-pass 53; by their adjustment the speed of closing the door can be adjusted and/or the impact of closing damped. `In the closing movement of the piston 16 the same covers in a. certain position an annular groove 62a in the cylinder 15 and thereby blocks the passage of liquid through the throttle 62, so that towards the end of the closing movement only the throttle 63 remains operative, which arrangement permits a very accurate regulation.

In order to prevent the pressure from'exceeding for any reason the permissible limit, a safety valve 64 (Fig. 8) is provided, the valve element 65 of which is pro- -vided with longitudinal grooves 66 and a sealing flange 67. Bye spring 68 the tension of which may be Vad'- justed by'a screw 7i) engaging a tapped bushing 69, the sealing flange is forced on a corresponding seat. In case-excessive pressure is reached, the sealing flange is lifted olf its seat against the spring bias, and hydraulic fluid can flow off through the longitudinal grooves 66 into the Vreservoir .43 relieved of pressure.

The suction space 71 (Fig. 3) of the cylinder 15 is in communication with the pressureless reservoir 48 through a non-return'valve (arranged in a conduit72) having a of the-cylinder. The suction chamber`71 is moreover in communication with the pressureless nreservoir 48 through a valve 74 which permits a discharge of liquid from the suction space 71 into the reservoir 4S when the door is being opened, i. e. when the piston moves from the right to the left, and the non-return valve with ball 73 closes. This valve 74 is so designed that it closes in a pre-determined position of the piston 16 which can be adjusted in a continuous manner on the valve itself; since no liquid can then escape any more from the suction space 71, the piston 16 can no longer move towards the left, i. e. the door is opened up to an adjustable opening angle only.

The valve 7 4 is a slide valve which has as its slide element a sleeve 75 which is slidable in a bore 76 forming its guide in the piston 16, and which is provided with holes 77. A spring 78 forces the sleeve 75 towards the left as far as an abutment 79 permits. The valve 74 has moreover an adjustment spindle formed by an abutment screw 80. Depending on how far the end 80a of the spindle 89 projects into the suction space 71, the sleeve 75 abuts on the same sooner or later during the opening movement of the piston 16; during the subsequent movement of the piston the said sleeve is then shifted to the right, so that the holes 77 enter into the bore 76, and the passage of liquid through the same is prevented. In order to prevent liquid hammer the edges of the holes 77 are chamfered so that this valve closes very gently.

vWhen the piston 16 cornes to a standstill owing to the closure of the valve 74, the opening of a non-return valve 81 allows any liquid still discharged by the pump 45 into the pressure chamber Sil of the cylinder 15 to flow olf from this space. The valve element of this non-return valve is formed by a closure bail 82 which is arranged, similarly to that of the valve 74, in a bore 83 of the piston 16. When during the opening movement of the piston the push rod 84 abuts on the end 85a of the adjustment spindel 85, the ball 82 is lifted off its seat against the pressure of the liquid, and allows the liquid to drain off into the pressureless reservoir 48 through an annular chamber 86, apertures 87 in the piston 16 and the interruption 15a of the cylinder wall 15.

By adjustment of the control spindles 80, it can be attained that the door remains open-without oscillations or jerks, at any aperture angle desired, as long as the motor 10 is energisedby the control apparatus. Then the angles at which the two valves are to be opened and closed, respectively, should be adjustedat least approximately to the same value, the fine adjustment depending on the speed of opening, the mass of the door etc., as the case may be. As soon as the'current is-sWitched off by the control apparatus, the piston moves from left to right under the action of the spring 20, and the door is being closed, the manner of operation of the various Vthrottles and valves being disclosed in the preceding dcscription.

As a modification, the adjustment screw 80 itself may form the valve element, the seat of which would then be formed by a bore provided invthe'p'iston. In this case accordingly a needle valve would be used.

A continuous regulation could .also be attained', if the valve elements were arranged in-the'lids of thevcylinder instead of in the piston 16, and adjustable abutments cooperating with therend faces ofthe piston wereprovicled. .Such a design would, however be considerably more complicated. l

In Fig. l() a modification isV illustrated, in which the valves 74 and the nonreturn valve having the ball 73 are combined into a single structural unit 83..

The sleeve 89 is arranged slidably in the piston 16 like -the sleeve '75, and is provided with holes 90. A shoulder 91 forms a seat for a ball 92.V A perforated plug 93, which is screwed into thesleeve 89 limits the vmovement of the ball towards the left. yThe end V80a' of the control screw 80 abuts on an abutment bidge94 bridging over the' bore of the said plug, when .the piston vmoves towards the left, and displaces thelsleeve89 against vthe biaslof the spring 95 until the holes Y9i) Aare covered and consequently g no more liquid can emerge from the suction space 71 into the pressureless reservoir 48. By the fluid pressure in the suction space at the same time the ball 92 is forced on its seat 91.

At the beginning of the movement of the piston towards the right, the ball 92 is lifted o its seat 91, so that liquid can be sucked into the suction space through the sleeve and the bore of the plug 93. When then in the course of the movement the sleeve 89 returns under the action of the spring 95 into the position illustrated, part of the liquid is sucked also through the holes 90.

Fig. 11 shows a further modification of the valves. T he adjustment screw 85 and the push rod 84 guided in the piston 16 are coupled to one another by means of a coupling sleeve 96 and of coupling pins 97. Likewise the sleeve 98 guided in the piston 16, and the adjustment screw 80 are coupled to one another by means of a coupling ring 99 and of coupling pins 100. Thereby it is safely prevented that one of these valves may be operated unintentionally by a pressure rise in the space 71. The aforesaid couplings are not made rigid but with some play in order that slight misalignments of screw and Valve owing to inaccuracies in manufacture may not lead to jamming the latter.

A ball 101 performs the same function as the balls 73 (Fig. 4) or 92 (Fig. 10) in that it permits the liow of liquid from the reservoir 4S through the interior 102. ofY

the sleeve 98, the seat 103 of the ball and the bores 104i of the coupling ring 99 and the sleeve 98 into the space 71, even when the holes 105 of the sleeve 98 are covered by the piston 16.

The ball 82 which co-operates with the aforesaid push rod 84 has a rear abutment, no longer in the form of a bushing (not designated in detail in Fig. 3), but of a coiled spring 106 which in the completely relaxed condition leaves a small clearance to the ball for rising from its seat in order that the said ball may be lifted off its seat at the slightest lowering of the pressure in the space 50. The spring prevents the ball 82 from moving away too far from its seat, so that it may be pressed again on its seat immediately upon the creation of an excess pressure in the space 50. The use of a spring instead of a rigid abutment prevents with safety the movement of the piston 16 towards the left from being limited by the weak push rod, after the ball has been abutting on the stop, which push rod might be deformed and then lock the whole assembly.

In the case of manual operation of the door, the piston 16 may continue to move to the left, independently of the adjustment of the screws and S5, until its front end face (on the left in Fig. ll) abuts on the fixed stop 107 of the lid 26a of the cylinder.

While I have described herein and illustrated in the accompanying drawings what may be considered typical and particularly useful embodiments of my said invention, I wish it to be understood that l do not limit myself to the particular details and dimensions described and illustrated, for obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent, is:

1. A hydraulic door opener, comprising in combination: an electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a cylinder in uid communication with the said pump and a piston moveable in the said cylinder and arranged to be mechanically coupled to a door, the said electric motor when energised 'driving the said pump and the latter then supplying liuid under pressure to the said servo-motor in the sense of opening the door, a spring mechanically connected to the said servo-motor and biasing the said piston thereof in the sense of closing the door, a iirst valve in fluid communication with the pressure side of the said cylinder, a second valve in uid communication with the suction side of the said cylinder, each of the said valves having a valve seat and a valve member moveable relative to its seat in a direction parallel to the movement of the said piston in the said cylinder and adjustment means each in operative relationship to one of thesaid valves, one of the said adjustment means opening the said first-named valve upon the said piston reaching a predetermined position and thus allowing the vdischargerof fluid from the pressure side of the said cylinder, and the other one of the Vsaid adjustment means closing the said second-named valve at approximately the same position of the said piston and thus ,stopping the discharge of liuid from the suction side of the said cylinder, the said position of the servo-motor piston corresponding to an opening angle of the door pre-determined by the setting of the said adjustment means.

2. A hydraulic doorropener as claimed in claim l, comprising a lid of the said cylinder, the said valve members being located in the said piston, and the said adjustment members being formed by abutment screws located in the said lid. j

3. A hydraulic door opener comprising in fcombination: an electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a cylinder in liuid communication with the said pump, a lid closing one end of the said cylinder and a piston moveable in the said cylinder and arranged to be mechanically coupled to a door, the said electric motor when energized driving the said pump and the latter then supplying fluid under pressure tothe said servo-motor in the sense of opening the door, a spring mechanically connected to the said servomotor and biasing the pistonthereof in the senseV of closing the door, a first valve of the non-return type arranged in fluid communication with the pressure side ofthe said cylinder having a valve seat and a ,closure ball moveable relative to its seat in a direction parallel to the movement of the said piston in the said cylinder, an adjustment screw fitted in a tapped hole of the said lid, a push rod slidably mounted in the said piston in alignment with the said adjustment screw and the center of the said ball, the said push rod abutting on the said adjustment screw and lifting the said ball off its seat upon the said piston reaching a predetermined position thus allowing the discharge of fluid from the pressure side of the said cylinder through the said non-return valve, a second valve arranged in fluid communication with the suction side of the said cylinder and having a valve seat and a valve member moveable relative to its seat in a direction parallel to the movement of the said piston in the said cylinder, and adjustment means in operative relationship to the said second valve closing the same at approximately the same position of the said piston thus stopping the discharge of fluid from the suction side of the said cylinder, the said position of the servo-motor piston corresponding to an opening angle of the door predetermined by the setting of the said adjustment screw and of the said adjustment means.

4. A hydraulic door opener comprising in combination: an electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a` plying fluid under pressure to the said servo-motor' in.

the sense of opening the door, a spring mechanically connected to the said servo-motor and biasing the said piston thereof in the sense of closing the door, a rst valve of the non-return type arranged in uid communication with the pressure side of the said cylinder and having a valve seat and a closure member moveable relative to its seat in a direction parallel to the movement of the said piston in the said cylinder, adjustment meansY in in* operative relationship to -the said valve and opening theru same upon the said piston reaching a pre-determinedpfi s tion thus allowiugh? discharge of fluid froml the pressure ot Y the said cylinder;asecndalv 'arranged in fluidycornmunicationwithl lthe s'iictifri4 side of"the"`sa`id cylinderv and comprising ajsleeve' lrn'ouiited'iiz( 'the said: pistonslidablyp'parallel to Vvthe Adirection of; movement of the latter in the said/cylinder and'having'hles'tor'the passagevofwuid, an adjustment.scrw`tted`in'a tapped a spring operatively engaging thesaid"pistona'nd sleeve and ,biasing the same into a position in'which `the"said` holesvjclearthe said piston,Y the said adjustment screw pushing lthe Said .Sssgtf OSSQB f1..WhiCh the Sad holesnare covered by the saidpiston upon the said sleeve abuttingY` on the saidfadjusltment screw in appro'xirii'ately the same position of the said pistonuas aforesaid, 'thus' stopping. the discharge. 0.f ..u.d ffsm the. Swivl Side f the said cylinder, ,the said positionnofvthe servomoto'r piston corresponding `tota/n,openingangle ofthe door predetermined by the ,setting lofuthe said adjustment rmeans and of the said adjustment screw. Y

5. A hydraulic.dooriopeneras claimed in claim 4,

comprising a ,closurebal l`jseated on a shoulder face ofU the said sleeve, anda plug, screwedwint'oV the said sleeve,

the said plugY having av longitudinal bore and limiting the movement of the said ball.` y' Y 6. A hydraulic door opener, 4 c :omprising indcombination: an electricmotor, anpumpi nrecluinically` .c oup'lpedw:k to the said electric motor, a hydraulick servo-motorhaving a cylinder in iluid communication withA the said pump and a piston moveable in the said cylinderrand arrangedto be mechanically coupled toa door, the said electric motor when energized driving the said pump, and the latter then supplying uid under pressure tothe saidY servo- K Y motor in the sense of opcningrthe door, a spring mechanically connected Vto the said servo-motor` and biasing the Y said piston Vthereof inthe sense of closing the door, a rstvalve of the non-return typeV arranged in `fluidrcornmunication with the pressure side of the said cylinder,

.and thus allowing the discharge of iluid from the pressure side of the said cylinder, and the other .one of the lsaid adjustment means closing the said second-named valve at approximately the same position of the said piston and thus stopping the discharge of iiuid from the suction side of the said cylinder, the said position of the servo-motor Y piston corresponding to an opening angle of the door predetermined by the setting of the said adjustment means, two regulating throttle valves arranged in parallel to one another, and a diiferential non-return valve arranged in series with the said two parallel regulating throttle valves, the said throttle valves and diflerential .non-return valve being arrangedV in, and controlling, the exhaust from the pressure side of the said servo-motor cylinder, permitting the discharge of fluid from the said pressure side upon the 'said pump coming to a standstill.

7. A hydraulic door opener as claimed in claim 6, com-k prising in addition: a liquid reservoir in .duid communication'withthe pressure side of the said servo-motor cylin-V der, another non-return valve arranged 1n and controlling the communication of the said reservoir with 'the said pressure side, and a safety valve in fluid communication withV thesaid reservoir, the said diiferential non-return valve also being in lluid communication with the said reservoir. v Y' 8. A hydraulic door opener as claimed in claim 6, Vcom-l of the said cylinder during a closure movement ofthe said piston. l e

` 9. Ahydraulic door opener comprising in combinai. tion: an electric motor, a pumpmechanically coupled' i" to the said electric motor, a hydraulic servomotor `having a cylinder having uidrcommunications with the said 'Y pump and a piston moveable in the said cylinder and mechanically coupled to the door, the said electric m'otor when energized driving the said pump andthe latterV then supplying fluid under pressure to the said servo motor in the sense of openingthe door, a spring mechanically connected to the said servo-motor and biasing the said piston thereof in the sense of closing the door,

control valves interposed in the said fluid communications, a casing having several parts and enclosing the electric motor, pump, hydraulic servo-motor valves,

and spring, and forming a reservoir for the hydraulic" lluid, at least one of the said fluid communications being formed by juxtaposed recesses in the contact faces of two adjacent parts of the said casing.

l0. A hydraulic doorvopener as claimed in claim 9, wherein the said juxtaposed recesses are formed by grooves in the contact faces of the said adjacent parts of the said casing.

l1. A hydraulic door opener as claimed in claim 9, wherein the said parts of the said casing enclose theV said electric motor, pump and servo-motor respectively, and comprising bolts passing through all of the said parts in common and tying the same together.

12. A hydraulic door opener as lclaimed in claim l1, wherein that part of theV said casing which encloses the said pump forms a mounting board having a bore in which both the said electricV motor and'pumpare journalled rotatably.

13. A hydraulic door opener as claimed in claim 1l, y wherein that part of the said casing which encloses the said pump forms a mounting board having a bore in which both the said electric motor and pump are journalled rotatably, at least one duct for the driving lluid'being i recessed in the said mounting board.

14. A hydraulic door opener as claimed in claim ll,

i comprising a detachable lid of the casing` part enclosing the said servo-motor cylinder.

l5. A hydraulic door opener, comprising in combination: an'electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a cyli j inder in tluid communication withV the said pump, and

prising in'addition a third non-'return valve in lluid corn-YY munication with the' suction side of the said servo-motor cylinder permitting 4liquid te. be suckedinw the. .Said gleam.

a piston moveable in the said cylinder and arranged to4 be mechanically coupled to a door, the said electric motor when energized driving the said pump and the latter then supplying fluid under pressure to the said servo-motor in the sense of opening the door, a spring mechanically connected to the said servo-motor and biasing the Vsaid piston thereof in the sense of closing the door, a ball seated in a bore yot" the said piston parallel to the move-V ment of the same, Va compression spring housed in the said bore ending a short distance from the said ball on the pressure side ofthe said piston, an adjustment screw screwed into the said cylinder inalignmcnt with the said bore, a push rod arranged in alignment with'and attached to the said adjustment screw and adapted to lift the said ball from its seat in the said Vbore at a4 certain position of the said piston from the pressure side towards the suction side of the said servo-motor cylinder, I

a valve in fluid communication with the said suction side of the said cylinder and having 'a valve seat and a valve Y member moveable relative to this seat in a direction paraliel to the movement of the said piston in the said cy1- inder, and adjustment means in operative relationslnp to thesaid valve, closing the same at approximately the j same position of the said piston as aforesaid and thus stopping the -discharge of iiuid from the said suction side of the said cylinder, the said positionof the servo-motor piston corresponding to an opening angle ofA the door 9 pre-determined by the setting of the said adjustment screw and the said adjustment means.

16. A hydraulic door opener comprising in combination: an electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a cylinder in fluid communication with the said pump and a piston moveable in the said cylinder and arranged to be mechanically coupled to a door, the said electric motor when energized driving the said pump and the latter then supplying fluid under pressure to the said servo-motor in the sense of opening the door, a spring mechanically connected to the said servo-motor, and biasing the said piston thereof in the sense of closing the door, a non-return valve arranged in uid communication with the pressure side of the said cylinder, an adjustment means in operative relationship to the said valve and opening the same upon the said piston reaching a pre-determined position and thus allowing the discharge of uid from the pressure side of the said cylinder, an adjustment screw screwed in the said cylinder in a direction parallel to the movement of the said piston in the said cylinder, a sleeve arranged in alignment with and attached to the said adjustment screw and guided slidably in a bore of the said piston, a ball-seat in the said sleeve, a ball seated on the said seat so as to move away from the said piston when leaving its seat, perforations being provided in the said sleeve on both sides of the said seat, the perforations on the side towards the said piston establishing uid communication between the suction side of the said cylinder to the pressure side thereof through the said sleeve while uncovered, the said last mentioned perforations being covered in the said bore of the piston at approximately the same position of the latter as aforesaid, the said position corresponding to an opening angle of the door pre-determined by the setting of the said adjustment means and of the said adjustment screws.

17. A hydraulic door opener comprising in combination: an electric motor, a pump mechanically coupled to the said motor, a hydraulic servo-motor having a cylinder in uid communication with the said pump, a piston moveable in the said cylinder and mechanically coupled to the door, a xed stop on the suction side of the said limiting the movement of the said piston from the pressure side of the said cylinder to the suction side thereof, the said electric motor when energized driving the said pump and the latter then supplying fluid under pressure to the said servo-motor in the sense of opening the door, a spring mechanically connected to the said servo-motor and biasing the said piston thereof in the sense of closing the door, a iirst valve arranging in fluid communication with the pressure side of the said cylinder, a second valve in fluid communication with the suction side of the said cylinder, each of the said valves having a valve seat and a valve member movable relative to its seat in a direction parallel to the movement of the said piston in the said cylinder, and adjustment means in operative relationship to one of the said valves each, one of the said adjustment means opening the first-named valve upon the said piston reaching a predetermined position in the said cylinder short of the said fixed stop and thus allowing the discharge of fluid from the pressure side of the said cylinder, and the other one of the said adjustment means closing the second-named valve at approximately the same position of the said piston and thus stopping the discharge of uid from the suction side of the said cylinder, the said position of the servo-motor piston corresponding to the limit opening angle of the door to be reached by automatic opening operation pre-determined by the setting of the said adjustment means, and the said xed stop limiting the aperture of the door by manually opening the same.

References Cited in the file of this patent UNITED STATES PATENTS 1,833,216 Hanna Nov. 24, 1931 1,993,612 Lum Mar. 5, 1935 2,233,521 Ernst Mar. 4, 1941 2,298,542 Potter Oct. 13, 1942 2,652,732 Frye Sept. 22, 1953 

